Some mechanical devices may be configured to have two discrete states with a respective associated operating position corresponding to each of the two states. The mechanical devices may be repeatedly cycled between the two states. For example, the two states may be designated as off/on, open/closed, extended/retracted, engaged/disengaged or some similar terminology.
Automobiles may include Shape Memory Alloy (SMA) actuators to operate such mechanical devices. SMA actuators may be a relatively simple, low mass alternative for fractional horsepower electric motors or similar electromechanical devices. SMA actuators take advantage of the ability of Shape Memory Alloys to repeatedly cycle between two positions as, for example, in a retractable air dam, a latch and a clutch, or to repeatedly cycle over a range of positions intermediate between predetermined limits, as for example in an adjustable louver array, a rearview or side mirror or a sun visor.